The present invention relates to an ink cartridge detector operable to detect whether or not an ink cartridge is properly mounted on a cartridge holder. The invention also relates to an ink jet printer provided with the above mentioned ink cartridge detector, and to the ink cartridge to be employed in the above mentioned ink cartridge detector.
There has been widely used an ink jet printer of a type that prints characters and images on a printing medium by discharging ink which is supplied from an ink tank onto the printing medium through a print head. In the ink jet printer of this type, the ink tank of a cartridge system (hereinafter referred to as an “ink cartridge”) has been widely employed so as to facilitate supply of the ink.
In the above described ink jet printer, it has been required to detect an amount of remaining ink in the ink cartridge and a mounting condition of the ink cartridge for the purpose of preventing defective printing due to shortage of the remaining ink in the ink cartridge or incomplete mounting of the ink cartridge, or for the purpose of issuing an alarm indicating the shortage or the incomplete mounting. For this reason, there have been proposed mechanisms for enabling the amount of the remaining ink and the incomplete mounting of the ink cartridge to be detected by a single optical sensor of the reflective type (disclosed in Japanese Patent Publications Nos. 10-230616A and 9-174877A, for example).
In the above described detectors, a light beam is emitted from the optical sensor onto two reflectors (prisms) which are provided in a bottom of the ink cartridge, and the amount of the remaining ink and the mounting condition are detected on the basis of amounts of reflective light beams received from the reflectors. Specifically, the reflector for detecting the amount of the remaining ink is transparent so that reflectivity (intensity of reflected light) may vary according to the amount of the remaining ink, while the reflector for detecting the mounting condition is mirror-finished so that the light can be reflected irrespective of the amount of the remaining ink.
However, in the above described related-art ink jet printer, there have been such problems as described below.
i) It has been necessary for the ink cartridge to be provided with two reflectors which are formed of separate members, and hence, the number of components and production steps are increased, creating a high cost for the ink cartridge.
ii) Because the reflectors of the ink cartridge are exposed inside the printer even when a printing operation is performed, there has been such a possibility that spots such as ink splashed during the printing operation might adhere to the reflectors to make the detection by the optical sensor unstable.
iii) When the optical sensor has received the reflective light, it is decided that the ink cartridge has been properly mounted. Therefore, when the optical sensor has received an exterior turbulent light, it has been liable to be decided that the ink cartridge has been properly mounted, even though the ink cartridge has not yet been mounted. As such, the printing operation might be commenced without proper mounting of the ink cartridge.